Search for fundamental physics with H.E.S.S. & CTA Christian - - PowerPoint PPT Presentation

Search for fundamental physics with H.E.S.S. & CTA Christian Farnier

Oskar Klein Centre – Stockholm University

WIN2013 Natal, Brazil September, 16th - 21th

Christian Farnier WIN2013 – Natal, Brazil 2

OUTLINE

 VHE astronomy  Imaging Atmospheric Cherenkov Telescopes  Few results on the search for fundamental physics  Conclusion

Christian Farnier WIN2013 – Natal, Brazil 3

γ-ray astronomy : probing the non-thermal Universe

PWN Pulsar SNR SNR Binary GRB AGN Galaxy cluster ? Axion ? DM ? Starburst galaxy

Galactic sources Extragalactic sources

Christian Farnier WIN2013 – Natal, Brazil 4

Detecting γ-rays



Convention HE : High Energy (E ≥ 100 MeV)

VHE : Very High Energy (E ≥ 100 GeV)



γ-rays are not deflected by B →study of sources and production mecanisms



Atmosphere is opaque to γ-rays Satellite exp. for HE

IACTs for VHE (very low fluxes 10-(11-12) ph cm-2 s-1) VHE, HE

Christian Farnier WIN2013 – Natal, Brazil 5

Imaging Atmospheric Cherenkov Telescope (IACT) principle

Backgrounds:

• the night sky (stars, Moon, …) : duty cycle ~1000h/y
• Charged cosmic rays (p,e,...) rate x105 higher than the brightest TeV γ-ray source.

Credits : W. Hofmann

Christian Farnier WIN2013 – Natal, Brazil 6

IACT principle (cntd)

Cherenkov photons production. Shower development recorded in the focal plane. Ultra fast (~10ns) acquisition camera. Image parameters reco. (direction, energy) Image based event selection / background rejection.

Christian Farnier WIN2013 – Natal, Brazil 7

IACTs - Stereoscopic system

In the current experiments, up to 5 IACTs are put together, allowing to

• bserve the same shower from

several point of view. Advantages :

• Improved bckg rejection (muons)
• Incoming direction degeneracy

dispelled

• Improved angular resolution
• Improved energy resolution

+ new shower reconstruction algorithms developped based on intrinsic 3D shower properties.

Christian Farnier WIN2013 – Natal, Brazil 8

Census of IACT experiments

HESS MAGIC CANGAROO (ended) VERITAS FACT

Christian Farnier WIN2013 – Natal, Brazil 9

The most advanced : H.E.S.S. 2

∅: 13m Camera :1 ton, 960 PMTs Begining of operation : 2004

4x Phase 1 : Phase 2 : + 1

∅: 28m Camera :2 ton, >2000 PMTs Begining of operation : 09/2012

Christian Farnier WIN2013 – Natal, Brazil 10

H.E.S.S. astrophysical results

H.E.S.S. galactic sources + 19 extragalactic sources

Christian Farnier WIN2013 – Natal, Brazil 11

CTA - Cherenkov Telescope Array



27 countries



> 1000 scientists

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2 arrays



3 types of telescopes

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Currently in the preparatory phase

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Construction phase will start in 2014

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>1000 sources expected



~ 1000h obs/y

Christian Farnier WIN2013 – Natal, Brazil 12

CTA : the ''perfect'' stereoscopic system



The most advanced stereoscopic systems have

• nly 5 (4) telescopes H.E.S.S. (VERITAS).



CTA will have dozens (to cover an area O(km^2)), most probably of 3 (or 4) different sizes :

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Large : 24m

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Medium : 12m

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Small : 6-8m

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Which will allow cover broader energy range and improve the performances :

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Angular & energy resolutions,

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Background rejection,

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Sensitivity,



….

CTA consortium 2012

Christian Farnier WIN2013 – Natal, Brazil 13

CTA observatory

First open observatory in the VHE domain Large number of users from different fields of science

Christian Farnier WIN2013 – Natal, Brazil 14

Some searches for fundamental physics :

1.Dark matter 2.Axion-like particles 3.Lorentz Invariance violation 4.Primordial black holes

Christian Farnier WIN2013 – Natal, Brazil 15

• 1. Dark matter in the Universe – really ?

Fritz Zwicky, 1933: ”If this

• ver-density

is confirmed we would arrive at the astonishing conclusion that dark matter is present with a much greater density than luminous matter.”

Coma galaxy cluster

Bergstrom, Rep. Prog. Phys. 2000 Clowe et al., 2006

YES ! At all scale.

Planck, 2013

Christian Farnier WIN2013 – Natal, Brazil 16

γ-ray flux from WIMP annihilations



Astrophysic factor :

 determine the nb of

annihilations → intensity of gamma-rays

Uncertainties :

 density profile, diffusion,

absorption,...



Particle physic factor :

 determine the nb of γ-ray

produced per annihilation → spectral shape

Uncertainties :

 cross section, mass,

branching ratios,...

Christian Farnier WIN2013 – Natal, Brazil 18

DM targets for indirect γ-ray searches

Pros: high DM density Cons: large uncertainties, several std γ-ray accelerators Galactic Centre Dwarf galaxies Pros: increasing number of objects, bckg free Cons: amount of DM limited Galactic Halo Pros: large integration region, DM profile well estimated Cons: bckg Extragalactic Galaxy Clusters Pros: number of sources, large amount of DM Cons: distance, bckg Pros: large integration region Cons: low DM density, bckg

N

• t

c

• v

e r e d i n t h i s t a l k

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Dwarf spheroidal galaxies

H.E.S.S. MAGIC Fermi Veritas

Dwarf galaxies probed in gamma-rays as in 2012

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Why dwarf galaxies ?



DM dominated (M/L ~ 10 – 100)

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Nearby (~100 kpc)

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Low background (ordinary matter content very low)

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Stellar velocities can be used to estimate DM density (error can be propagate to particle constraints)

Christian Farnier WIN2013 – Natal, Brazil 21

H.E.S.S. results

Carina dSph Sculptor dSph Sagittarius dSph



Signal search : ON (target region) - OFFs (CR bckg determination)

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Flux upper-limit determination : ΦUL = f(Nobs, Aeff, Tobs, DM model(mDM))

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Correspondance into annihilation cross-section : <σv>UL = f(ΦUL, DM model(mDM), J)

H.E.S.S. Coll, 2007-2011

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Prospects



H.E.S.S. II and CTA will be more sensitive thanks to lower energy threshold



Exemple : CTA – 100h Classical vs ultra-faint dSph



Still above the thermal relic density



But stacking will also improve our results, see Fermi-LAT results Similar analysis currently ongoing in H.E.S.S.

CTA consortium 2012 Fermi collab, 2011

Christian Farnier WIN2013 – Natal, Brazil 23

The Galactic halo with H.E.S.S.

Most constraining results on the DM searches for large massive particles (mWIMP ~ 400 GeV). But still above viable DM models. Better sensitivity is required.

H.E.S.S. collaboration, 2011

signal, bckg and excluded regions definition Corresponding DM densities Observation results : no significant excess

DM density vs distance from the GC Observation regions γ-like events spectrum Tobs = 112h

Christian Farnier WIN2013 – Natal, Brazil 24

CTA prospects

• Increased FOV → larger difference of DM content between ON and OFF regions
• Simulations indicates that the Galactic halo is the most promising location for CTA

indirect DM search.

• In only 50h of observations, CTA will probe SUSY models compatible with WMAP

results. 5°

CTA consortium 2012

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H.E.S.S. Coll. 2013

Line search with H.E.S.S.

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Integration region similar to halo analysis

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Data set :

4-tel. events (∆E/E), 2004-2007 [112h] (Eth)

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No OFF subtraction

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Bckg (« g-like » CRs) spectrum fitted

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Profile likelihood search of a line-like signal

• n top of background

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H.E.S.S. II prospects

H.E.S.S. Coll. 2013 HESS coll. 2013 Bergström, Bertone, Conrad, CF, Weniger., 2012

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And next with CTA

CTA expectations



Confirmation of Weniger (2012) line >5σ in 5h [syst. uncertainties]



1 vs 2 lines distinction reachable with additional time and refined analysis

Bergström, Bertone, Conrad, CF, Weniger., 2012

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Not only gamma-rays !

H.E.S.S. coll., PRL 2008 & A&A 2009

Search for electrons (+positrons)

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Extragalactic regions (low gamma-ray content)

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Large collection area and exposure time

Analysis and results

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Electron identification from simulations + Random Forest

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Power-law + break @ 1 TeV

Disproved ATIC peak and its DM interpretation

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• 2. Axion-like particles

Same phenomenology as true axion (Peccei & Quinn, 76) but ma and gγa unrelated γ/ALP oscillations in external magnetic field... ...possible modification of opacity of the Universe to TeV gamma-rays. Important for very distant sources detected in gamma-ray.

Wouters & Brun, PRD, 2012

Conversions γ/ALP introduce irregularities in gamma-ray spectrum

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amplitude driven by gγa

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location driven by ma

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Axion-like particles H.E.S.S. results

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Search for irregularities in PKS2155 flare spectrum

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Look for anomalous deviations in triplet

• f successive bins

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Statistical analysis on MC

L ↔ size of conversion domain s ↔ coherence length

H.E.S.S. collab. submitted

Christian Farnier WIN2013 – Natal, Brazil 31

• 3. Lorentz Invariance Violation

Motivation

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Test LI predicted to be violated @~Planck scale in some QG theories → absence of LIV can help discards models

Speed of light dispersion Context



Consider 2 photons of ≠ E1, E2 emitted at same time but observed at t1 and t2 c '=c(1±ζ E EP ±ξ

2 E 2

EP

2)

Δt Δ E≈ ζ EP H 0∫

z

dz ' (1+ z')

√Ωm(1+z ')

3+ΩΛ

Δt Δ E

2≈

3 ξ 2 EP

2H 0∫ z

dz' (1+z ')

2

√Ωm(1+z ')

3+ΩΛ



Small effect can add up over cosmological distances and lead to signficant delays → use of variable and distant sources (GRBs, AGN flares)

Christian Farnier WIN2013 – Natal, Brazil 32

Lorentz Invariance Violation H.E.S.S. results

PKS2155 exceptional flare of 2006



Signal dominated (300σ)

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High flux variability

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No spectrum variability

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z=0.116

200 < E < 800 GeV E > 800 GeV

H.E.S.S. collaboration, PRL 2008 & AstrPh 2011

Lags ?

Results (from event-by-event likelihood analysis [H.E.S.S., Astr.Ph 2011]):



No significant lags → 95%CL UL on QG scale Linear term : El

QG > 2.1x1018 GeV

• Quad. Term : Eq

QG > 0.6x1011GeV

→ Best limits with AGN

Christian Farnier WIN2013 – Natal, Brazil 33

Lorentz Invariance Violation Prospects : H.E.S.S.II & CTA

H.E.S.S. II



Increased energy range to lower energy (Eth ~ 30GeV) → bigger lever arm for ∆E

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Faster repositioning of the large size telescope → Observation of GRBs at VHE ?

CTA



Increased energy range (both side)



x10 better sensitivity & pointing modes dedicated to transient source detection → AGN population study (better understanding of source effect – time-dependant model)

Pulsars



VERITAS detection of Crab pulsar @ 200GeV. More to come ? + pulsars are perfect astronomical clocks

• nearby object

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• 4. Primordial black holes

PBH as source of gamma-rays

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BH created in the early Universe

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Evaporation through Hawking's radiation

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Lifetime is related to MPBH (sensitive to MPBH O(1014g))

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Progenitor for some GRBs ?

Gamma-ray search

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Hypothesis : BH atmosphere negligible (otherwise strong energy cut off)

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Evaporation is a runaway process : burst of gamma-rays expected in final stage

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Search for number N = ∂ρ/∂t x Veff of events in time window ∆t within the HESS PSF

Average number of photons from a PBH explosion detectable by H.E.S.S. as a function of the distance to the burst, for several values of the remaining time before explosion ∆t.

P R E L I M I N A R Y

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Primordial black holes

Method



Search for correlated events in space and arrival time

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Background estimates through « scrambling »

Data set

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2004-2012 (~2600h)

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Events within 2deg of camera FOV

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PSF=0.1deg

Results

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No significant deviation from bckg expectation → 95 % CL UL : ρ/ ∂ ∂t < 1.4 x 104 pc-3y-1

Prospects



Thanks to lower energy threshold H.E.S.S.II and CTA will allow to probe models PBH with atmosphere

Christian Farnier WIN2013 – Natal, Brazil 36

Conclusions



IACT experiments have entered into a new era :

 Already >140 sources detected @ VHE  H.E.S.S. II has been inaugurated 1 year ago, new results are

soon to come

 The CTA observatory, will enlarge this window of the Universe

recently opened and allow to discovered ~10 times more sources



IACTs are multi-purpose, multi-channel experiments



They can bring a lot of new information to questions of fundamental physics

Christian Farnier WIN2013 – Natal, Brazil 37

Thank you for your attention !

Christian Farnier WIN2013 – Natal, Brazil 38

Christian Farnier WIN2013 – Natal, Brazil 39

H.E.S.S. view of the GC

Aharonian et al., 2006 Aharonian et al., 2006 After point-like sources removal H.E.S.S. view of the GC

DM interpretation unlikely both from the signal morphology and its spectral shape. DM signal search difficult due to the observed emission.